1. Field of the Invention
This invention relates to a method, a computer program, and an apparatus for recording information signals on a recording medium having at least two signal recording layers. Also, this invention relates to a method, a computer program, and an apparatus for reproducing information signals from a recording medium having at least two signal recording layers. Furthermore, this invention relates to a method, a computer program, and an apparatus for recording and reproducing information signals on and from a recording medium having at least two signal recording layers.
2. Description of the Related Art
Optical-disc apparatuses include a DVD player, a DVD recorder, a combination of a DVD player and a DVD recorder, and a personal computer provided with a DVD drive and a software for recording and reproducing an information signal on and from a DVD via the DVD drive.
A typical optical-disc apparatus handles an information signal containing at least one of video information and audio information. The video information represents, for example, a movie. The audio information represents, for example, music.
The typical optical-disc apparatus operates as follows. During a recording mode of operation of the apparatus, an original information signal is compressed into a compression-resultant information signal. An optical pickup (an optical head) in the apparatus records the compression-resultant information signal on an optical disc. During a playback mode of operation of the apparatus, the optical pickup reproduces a recorded information signal from an optical disc. The reproduced information signal is expanded into an original information signal.
Japanese patent application publication numbers 2001-167519 and 2001-283513 which correspond to U.S. Pat. No. 6,285,632 B1 disclose an optical-disc apparatus able to handle a plurality of information signals including a first information signal and a second information signal.
The optical-disc apparatus in Japanese applications 2001-167519 and 2001-283513 operates as follows. During a plural-signal recording mode of operation of the apparatus, plural original information signals are compressed into plural compression-resultant information signals respectively. An optical pickup (an optical head) in the apparatus records the plural compression-resultant information signals on an optical disc on a time sharing basis. During a plural-signal playback mode of operation of the apparatus, the optical pickup reproduces plural recorded information signals from an optical disc on a time sharing basis. The plural reproduced information signals are expanded into plural original information signals respectively. During a signal recording/playback mode of operation of the apparatus, a first original information signal is compressed into a first compression-resultant information signal. The optical pickup records the first compression-resultant information signal on an optical disc and reproduces a second recorded information signal from the optical disc on a time sharing basis. The second reproduced information signal is expanded into a second original information signal.
The optical-disc apparatus in Japanese applications 2001-167519 and 2001-283513 includes a buffer memory provided between the optical pickup and an encoder/decoder for signal compression and expansion. The buffer memory has divided areas for temporarily storing the respective information signals transmitted between the optical pickup and the encoder/decoder. The bit rate of signal transfer to and from an optical disc differs from the bit rates of compression-resultant information signals outputted from the encoder/decoder and the bit rates of reproduced information signals to be inputted to the encoder/decoder. These bit rate differences are absorbed by the buffer memory. Each of the information signals transmitted between the optical disc and the buffer memory is divided into blocks having equal sizes (equal information amounts). The transmission of each of the information signals is on a block-by-block basis. For the simultaneous and continuous playback or recording of the information-signal contents, the sizes (the information amounts) of blocks of the respective information signals are decided on the basis of a given relation among parameters including seek times taken by the optical pickup to move among different optical-disc areas assigned to the respective information signals, and the above-indicated bit rates.
Basically, the optical-disc apparatus in Japanese applications 2001-167519 and 2001-283513 is designed to access different areas of one signal recording surface (one signal recording layer) of an optical disc during the plural-signal recording mode of operation, the plural-signal playback mode of operation, or the signal recording/playback mode of operation.
There is a large-capacity optical disc which has two different recording layers.